Numerical simulation of the CO2 diffusion effect on low turbulent mixed convection in a ventilated room heated by the bottom

Abstract

A double-diffusive mixed convection within low turbulent regime in a ventilated cavities filled with an air CO2 mixture and heated from below has been numerically investigated. The lower wall was sustained at a uniform temperature and CO2 concentration. The vertical and upper walls were kept at external temperature and CO2 concentration. To analyze the behavior of flow, the ventilation effectiveness for temperature distribution and removal of CO2 contaminant, four configurations were dealt. These differ from each other by the location of the mixture inlet and outlet gaps. Likewise, three CO2 concentrations were considered (103, 2?103, and 3?103 ppm) to investigate the influence of the CO2 diffusion on the ventilation effectiveness. The numerical simulations were performed by considering closed Reynolds averaged-Navier-Stokes equations using the Reynolds-normalization group k-? model. The governing equations? set was then solved using the finite volume method, in which the pressure-velocity coupling was handled using the SIMPLEC algorithm. Validation of the numerical model was achieved by comparing our results with available experimental data. The obtained results indicate that the CO2 diffusion effect on the air movement and the ventilation effectiveness for temperature distribution can be neglected in the present study. However, the CO2 diffusion remains a key parameter in terms of indoor air quality index. Also, it was found that one of the studied configurations provides a better ventilation effectiveness to remove heat and CO2 contaminant, and insures a homogeneous temperature and CO2 concentration in the occupied zone. The three other configurations maintain an acceptable level of heat and can be used in temperate climate to ensure good indoor air quality.